Conventional electrical receptacles used in industrial, commercial and residential applications deliver electricity to a variety of electrical appliances. The receptacles manufactured today have a hard Lexan plastic enclosure and deliver a hot, neutral and ground to said electrical appliances via a plug which is inserted into three of the six holes in a typical grounded application. Voltage and current travel through the hot conductor to the appliance circuit. If the appliance circuit is switched on, the voltage and current flow through to the neutral conductor completing the circuit. The circuit has an inherent resistance associated with the appliance load demand whereby the resistance determines the load requirement. If there is no resistance in the circuit, it is a short between the hot conductor and neutral conductor and if the resistance is infinite then there is an open short on one of the conductors. The description set forth in this patent describes in sufficient detail a circuit which determines these conditions of resistance before delivering the voltage and current to the hot conductor of the appliance and it is understood that various electronic designs changes could be made without departing from the scope or the spirit of the related art.
Electrical receptacles configured to eliminate arc faults rather than merely detect such faults with attendant circuit disconnection; the invention contemplates low-cost, child-safe electrical receptacles useful in residential situations and which can be fitted within the confines of single gang enclosures. The safety receptacles of the invention can be used in all use situations including residential, commercial and industrial applications to increase safe use of electrical receptacles in residential applications in particular and to decrease industrial liabilities. In essence, the safety receptacles of the invention prevent arcing during insertion of a plug into the receptacle, during residence of the plug in the receptacle and during removal of the plug from the receptacle with a substantial load to the receptacle while determining the load demand does not exceed the receptacle's electrical specification.
An arc fault circuit interrupter (AFCI) is a circuit breaker designed to prevent fires by detecting non-working electrical arcs and disconnect power before the arc starts a fire. Advanced electronics inside an AFCI breaker detect sudden bursts of electrical current in milliseconds, long before they would trip a regular overcurrent circuit breaker or fuse. The AFCI should distinguish between a working arc that may occur in the brushes of a vacuum sweeper, light switch, or other household devices and a non-working arc that can occur, for instance, in a lamp cord that has a broken conductor in the cord from overuse. Arc faults in a home is one of the leading causes for household fires.
AFCIs resemble a GFCI/RCD (Ground-Fault Circuit Interrupt/Residual-Current Device) in that they both have a test button, though it is important to distinguish between the two. GFCIs are designed to protect against electrical shock, while AFCIs are primarily designed to protect against fire
Starting with the 1999 version of the National Electrical Code in the United States and the 2002 version of the Canadian Electrical Code in Canada, AFCI are now required in all circuits that feed receptacles in bedrooms of dwelling units. The National Electrical Code is an industry consensus document adopted by many U.S. municipalities. This requirement of the NEC is typically accomplished by using a kind of circuit-breaker (defined by UL 1699) in the breaker panel that provides combined arc-fault, ground-fault, and over-current protection. The ground-fault protection is intended to prevent fire from arcs to ground and works at a higher threshold (30 mA) than the GFCI/RCD (Ground-Fault Circuit Interrupt/Residual-Current Device) implementations protecting against the safety hazard of electric shock (which operate at 6 mA). Combined devices are available which trip at the lower, 6 mA threshold of a true GFCI/RCD.
Even AFCI's do not, however, provide protection against all of the possible circuit faults that could ignite a fire. In particular, they provide no special protection against so-called “glow faults” where a relatively low-resistance short circuit draws a modest amount of current (within the trip limits of the circuit breaker) but heats the localized area of the fault to red heat. Glow faults also can occur where a connection in series with a load suddenly develops a high resistance; this might be the result of a now-defective switch, socket, plug, or wire connection (series faults are observed with special frequency in aluminum wire junctions). No practical circuit breaker could detect either such fault as there is no measurable characteristic that any circuit breaker could employ to distinguish a glow fault from the normal operation of a branch circuit.
Power outlets or receptacles are designed for power distribution through out various structures around the world and are designed with ease of manufacturing and installation design standards. If a short by a conductor is connected between the Neutral and Hot side of a receptacle, the said receptacle will arc, possibly causing fire or electrocution. In the patent Chapman et al; U.S. Pat. No. 6,678,131: Arc-safe electrical receptacles the use of a “Quench arc circuit” is utilized to reduce the arc between the contact points whereby said contact points are bypassed by aforementioned capacitor based quench arc circuit. Closely examining the circuit, one can determine the hot side of the quench arc circuit would short to ground causing discharge of electrical flow prior to contact closure.
Electrical receptacle outlets in walls and floors may present shock and electrical fire hazards to consumers. The U.S. Consumer Product Safety Commission estimates that 3,900 injuries associated with electrical receptacle outlets are treated in hospital emergency rooms each year. Approximately a third of these injuries occur when young children insert metal objects, such as hair pins and keys, into the outlet, resulting in electric shock or burn injuries to the hand or finger. CPSC also estimates that electric receptacles are involved in 5,300 fires annually which claim 40 lives and injured 110 consumers. Outlets with poor internal contacts or loose wire terminals may become overheated and emit sparks. Even a receptacle with nothing plugged into it may run hot if it is passing current through to other outlets on the same circuit. To prevent damage to receptacles, appliances should be switched-off before unplugging from a receptacle.
The present invention is aimed at one or more of the problems described above.